U.S. Pat. No. 3,648,768 has disclosed heat exchanger elements of plastic material consisting of a plurality of parallel pipes having connecting webs maintaining the pipes transversely spaced apart, which elements can be manufactured in one piece. It is stated in this document that the elements should be designed to have an inherent static stability for all practical purposes, more specifically sufficient bending strength to allow the elements supported at their ends to bridge a distance of several meters without bending. When multiple elements of this type are combined so as to form a larger heat exchanger block, spacing members are used whose opposite sides conform to the contours of one side of each of two adjacent heat exchanger elements. These spacing members may be e.g. glued or welded to the respective elements. Mechanical connecting means such as rivets, screws and tie rods may also be used. The elements may be connected to headers by cutting out the ends of the connecting webs so that short individual pipe ends project from the remaining main body of the connecting webs. These pipe ends may be fitted into bores of the header or anchored therein using short nipples. Due to the design this known heat exchanger having a heat exchange block comprising multiple elements of this type is a cross-flow heat exchanger.
A significant disadvantage of this known device is that although the elements are said to be thin-walled, relatively thick walls are required in heat exchangers of industrial scale, thereby severely limiting heat transfer between the fluids. Furthermore, despite the fact that the elements may be manufactured in one piece, a laborious operation whether by (physico)chemical means whether by mechanical means is needed to assemble several elements into a large heat exchange block.
Furthermore a compact countercurrent heat exchanger is for example known from US 2005/0217837. In this known heat exchanger a plurality of longitudinally extending and parallel fluid carrying tubes are arranged in thermal contact with one another. According to this publication each tube has at least one bend congruent to a bend in an immediately adjacent tube. All tubes are manufactured separately and then assembled together using for example Ag based alloy for brazing. During use a first heat exchange fluid flows through any one tube in a direction opposite to a direction of a second heat exchange fluid that flows through an immediately adjacent tube. In such a way a counter-flow heat exchange relation between the first and second heat exchange fluid is achieved. From the context of the specification it is apparent that such a compact counter-flow heat exchanger is obviously intended for use in aerospace dynamic power systems. In this known device the heat exchanger tubes are made from stainless steel.
Heat exchangers made from metal as in US 2005/0217837 are subject to fouling. Furthermore corrosion of the metal from which the heat exchanger channels are made may cause problems depending on the nature of the fluids between which heat is to be exchanged. Improvement with respect to corrosion may be achieved by using more expensive, more corrosion resistant metals or alloys such as stainless steel.
U.S. Pat. No. 4,733,718 has disclosed heat exchanger bodies or heat accumulator bodies for application according to the recuperator or regenerator principles. Such a body comprises a stack of extruded hollow chamber panels made from plastic and having plane smooth outer walls and webs that join the outer walls in a single piece. It is said that the plastic must be resistant to the media which, in use, will flow through the chambers of the hollow chamber panels. The softening temperature of the plastic should be above the highest operating temperature. The advantages claimed of this known heat exchanger body made up of a stack of individual hollow chamber panels are that the construction costs and expenses are low. The examples of individual hollow chamber panels shown in this document comprise a plastic body of one row of four adjacent hollow chambers. Several of these panels can be stacked to form the heat exchanger body. The joining of these panels in the area of the front surfaces thereof can be produced by welding, gluing or mechanically e.g. using clamping elements. Interlocking elements co-operating with elevations and/or depressions in the outer surfaces of the front surfaces of the panels are preferred. Disadvantages of this known heat exchanger relate to the double wall thickness affecting heat transfer, the square cross-section being a source of sealing problems and difficulties encountered in separately feeding the chambers. Furthermore, although the single panels can be manufactured easily, assembling multiple elements into a stacked configuration is laborious. The manufacturing process of the panels may become more complicated, if interlocking parts should be present in the panels themselves.
WO 2005/071339/discloses a heat exchanger for heat exchange between oil and water. An embodiment of this known device comprises rows of interconnected modules. Each module comprises a longitudinal tube having fins and two diametrically arranged connectors allowing assembling multiple modules into a linear row of modules. A separation plate is provided as a support between rows of interconnected modules. A first fluid flows through the longitudinal tubes, while a second fluid flows in the space between the modules and the housing and/or separation plates of the heat exchanger.
It is obvious that the designs and assembling processes discussed above are complicated, cumbersome, laborious, time-consuming and therefore expensive, offering a suboptimal final product with respect to its final heat transfer properties.